Field of the Invention
The invention relates to a method for manufacturing an adjustment fitting, in particular for a motor vehicle seat, having an outer wheel with internal teeth that can be associated with a first fitting part, and having an inner wheel with external teeth that can be associated with a second fitting part, wherein the inner wheel with external teeth is inserted eccentrically to an axis of rotation, in the manner of a wobble mechanism, in the outer wheel with internal teeth, wherein eccentric cam parts forming a variable eccentricity are placed to be rotatable with respect to one another in an eccentric receiving space formed between the axis of rotation and the inner wheel, wherein a transmission element having engagement elements for actuating the eccentric cam parts is employed such that the engagement elements works together with carrier elements of the eccentric cam parts.
Description of the Background Art
An adjustment fitting of the aforementioned type is typically used for adjusting the backrest of a motor vehicle seat, in particular. To this end, the first fitting part is attached to the backrest and the second fitting part is attached to the seat base of the vehicle seat, for example. The use of a wobble mechanism has proven its value in this location, since it represents a rotary joint that requires comparatively few elements while simultaneously having a transmission.
An adjustment fitting of the aforementioned type is known, for example, from DE 29 21 588 A1, which corresponds to U.S. Pat. No. 4,407,544. The wobble mechanism in this design comprises an outer wheel with internal teeth that is rotatable about the axis of rotation, and an inner wheel with external teeth that is located eccentrically to the central axis in the interior of the outer wheel. The outer wheel and inner wheel here form an eccentric receiving space with regard to one another, in which space are located a first and a second eccentric cam part that are rotatable relative to one another, by which means a variable eccentricity is formed. A carrier plate that can be rotated by means of an adjusting shaft is provided for actuating the wobble mechanism. The carrier plate has recesses that stand in engagement with carrier pins located on the eccentric cam parts. In addition, a mechanically acting coupling element (for example a spring) is provided that, in the rest position of the adjustment fitting, rotates the eccentric cam parts relative to one another so that their overall eccentricity increases. By this means, the planetary wheel is brought into a position in which it engages the outer wheel without play. When the carrier plate is rotated, one eccentric cam part at a time is rotated by means of the carrier pin, reducing the overall eccentricity. By this means, the inner wheel is brought into a position in which it engages the outer wheel with play. The inner wheel can be rotated relative to the outer wheel in a wobbling manner with rotating eccentricity by means of the carrier plate. By this means the first fitting part rotates relative to the second fitting part with a corresponding transmission ratio that is determined by the ratio of the tooth count of the external teeth of the inner wheel to the tooth count of the internal teeth of the outer wheel.
For manufacturing reasons, the individual parts of the adjustment fitting always have deviations from the norm with respect to their geometric parameters. Certain manufacturing tolerances are thus always present in the individual parts. Actuation of the wobble mechanism by the carrier plate in the adjustment fitting described above is strongly dependent on component geometry, however. Consequently, even small tolerances in manufacture can result in the wobble mechanism or adjustment fitting having switchover clearance and loss angle.
Furthermore, the elements of the carrier plate and their control geometry are constructed to act on only one side. This means that in a design of the eccentric cam parts that is not self-locking, they may open under load. The limits within which the eccentricity is adjustable are in turn limited by the tolerances of the components. Accordingly, these manufacturing tolerances can result in a reduction in strength, excessive play under corresponding load, and non-uniform startup between the left and right adjustment fittings.
These problems have hitherto been dealt with through such measures as parts selection at assembly. This means that components that deviate similarly, as defined by the deviation of an individual part from the standard, and thus fit together better, are combined with one another to produce a wobble mechanism. For electrically driven adjustment fittings, an additional eccentric carrier ring that actuates the eccentric cam parts by friction is also sometimes included. These measures can merely reduce the above-described disadvantages resulting from manufacturing tolerances, but cannot eliminate them.